**Question:** If a 5-year-old child suddenly develops stridor, which one of the following would be the most likely diagnosis:

A. Epiglottitis
B. Foreign body aspiration
C. Tracheomalacia
D. Diverticulum of Kommerell

**Core Concept:**

Stridor is a high-pitched, harsh, and wheezing sound produced during inspiration and expiration. In children, this could be a sign of airway obstruction. In this context, we need to consider the possible causes of sudden airway obstruction in a 5-year-old child.

**Why the Correct Answer is Right:**

A. Epiglottitis (H. Influenzae): Epiglottitis is an acute inflammation of the epiglottis, caused by Haemophilus influenzae type b (Hib). This condition results in airway obstruction due to swelling and enlargement of the epiglottis. The correct answer is A as epiglottitis is a common and severe infection causing stridor in children, and especially in 5-year-olds.

B. Foreign body aspiration: A foreign body (FB) aspiration is a common cause of stridor and respiratory distress in children, especially when the child is playing and accidentally inhales a small object. A foreign body can obstruct the airway, leading to stridor. Foreign bodies can cause immediate or delayed stridor, depending on the size and type of the FB. However, this option seems less likely in a 5-year-old, as the other options are more specific to the age group.

C. Tracheomalacia: Tracheomalacia is a condition where the trachea becomes weak and collapses, leading to stridor, particularly in infants and young children. This option is more suitable for a 5-year-old, making it the correct answer. Tracheomalacia is a congenital anomaly that can cause stridor in young children.

D. Diverticulum of Kommerell: A diverticulum of Kommerell is a rare blood vessel anomaly, and it is not a common cause of stridor in children. This option is less likely in a 5-year-old, making it the correct answer.

**Why Each Wrong Option is Incorrect:**

A. Foreign body aspiration: While foreign body aspiration can lead to stridor, it is less likely in a 5-year-old since the correct answer (C) is more specific to the age group.

B. Foreign body aspiration: Similar to option B, this option is less likely in a 5-year-old due to the presence of correct answer C, which is more suitable for this age group.

D. Diverticulum of Kommerell: As mentioned above, this condition is rare and not a common cause of stridor in children, making it less likely in a 5-year-old.

**Clinical Pearls:**

1. In children, stridor should raise suspicion of airway obstruction, and the diagnosis should be confirmed by clinical examination and imaging.
2.